In current eye examinations, the techniques utilized can be referred to as either direct or indirect ophthalmoscopy. Direct ophthalmoscopy is normally a principal part of every eye examination in which the examiner utilizes a conventional hand-held ophthalmoscope in order to examine the fundus. In accordance with such technique the examiner's eye is normally pressed to the the ophthalmoscope device and the instrument is placed as close to the eye as possible, usually less than 1 cm. Such technique permits close and direct examination of the fundus, i.e. a relatively narrow retinal region.
In order to access a wider retinal area, for example, when injury or disease is involved, indirect ophthalmoscopy is used wherein a relatively large lens is held approximately 5 cm. from the eye so as to provide an image of the fundus region at a location in which an appropriate camera can be used to photograph such image. Such cameras, characterized as "fundus cameras," normally require a special design to provide wide angle photography of a curved surface and provide a permanent record of the retinal appearance so as to permit a later more in-depth examination thereof.
In both instances an instrument must be placed relatively close to the patient's face, i.e., within a few centimeters, or less. With some patients, e.g. children, animals, or even wary adults, such technique can be unduly upsetting and can even cause a traumatic experience for the patient. Moreover, in order to photograph or provide some other permanent display of the fundus, it is necessary that the patient's head remain almost absolutely still since any motion, however slight, will tend to distort or destroy the image created. Moreover, in order to achieve the ability to see a wide region of the retina it is necessary to dilate the pupil by utilizing appropriate medication which produces mydriasis. In some instances in order to perform the examination the patient must be sedated or placed under firm restraint, techniques which severely restrict the opportunity for routine fundus examination.
Because of such disadvantages, it is desirable, particularly when examining an unanesthetized or unsedated infant, young child, animal, or a wary patient of any age, to avoid having to place any objects, and particularly medical instrumentation objects, at or near the patient's face. Further, it is desirable to provide an examination technique which permits some minor movement in the position of the eye during the examination procedure without unduly distorting the image achieved. Further it is desirable to devise a technique which permits an image to be formed of a relatively large region of the retinal area without the use of mydriasis so as to permit non-mydriatic fundus photography.